1. Field of the Invention
This invention relates to a waste processing machine; more specifically, to a waste processing machine incorporating a combination chipper, swing hammer and hog hammer.
2. Description of the Related Art
A variety of devices are provided to comminute and chip discarded waste products. Currently, four types of equipment are generally used for this purpose: chippers (disk and drum types), hammer mills, hogs and shredders. Shredders operate much slower than the other three types and are more suited for processing metals and rubber products.
Chippers are generally constructed around a rotating disk or drum. The chippers mount a plurality of blades to the rotating disk or drum and shear the wood products into chips. Hammer mills are generally constructed around a plurality of rotating disks having a plurality of free-swinging hammers attached at the periphery of each disk, providing for the transferring of a portion of the kinetic energy stored in the rotating disks to the wood products through the rotating hammers. Hogs are similar to hammer mills except that the hammers are rigidly secured to the periphery of the rotating disks. Hogs may also be constructed with a drum.
Of chippers, hammer mills and hogs, chippers are generally much more efficient, requiring less horsepower to chip the material while simultaneously being more productive. Chippers can chip logs and trees up to 40 inches in diameter, as well as small brush. They are also used to produce a dimensionally similar chip for the paper industry. A major disadvantage of chippers is that they require reasonably "clean" wood in order for the chipper knives to remain sharp. Any foreign material such as nails, spikes, rocks and sand will quickly dull the knife cutting edge. For this reason, chippers are not suited for reducing wood waste such as pallets, construction refuse or paper products.
A hammer mill will break up pallets, paper products, construction materials and small tree branches. The kinetic energy stored in the free-swinging hammers is used to break up the material. Because the hammers do not have the same requirement for sharp edges as chipper knives, dirty material is easily processed by a hammer mill. A hammer mill also has the advantage that the rotatable hammers will recoil backwardly if the hammer cannot break the material on impact. This built-in safety feature permits the hammers to protrude several inches beyond the disks that support them, making it possible for the hammers to make good contact with the material.
However, a known disadvantage of the hammer mill is that the size of the free-swinging hammers is limited. The hammers rely on centrifugal force to hold them in a radially outward position ready for impact. Upon impact, they may swing back rapidly which produces an unbalancing force on the mill. If the hammer mill turns too fast or the hammers are too heavy, a large vibration will occur. For this reason, the amount of kinetic energy that can be stored in the free-swinging hammers is limited. This, in turn, limits the size of the logs being processed to approximately 6 inches in diameter.
A hog is similar to a hammer mill except that the hog hammers are fixed to the disks or drum and do not rotate relative to the disk assembly. The hog has two advantages over the hammer mill. First, the disk assembly or drum always remains balanced because the hog hammers do not swing. Second, the hog hammer uses the full kinetic energy that is stored in the rotating disk assembly or drum to do the work on the waste products. Normally, the stored energy in the disk assembly or drum is far greater than the stored energy in the free-swinging hammers. Typically, logs up to eight or 9 inches in diameter can be processed with a hog. The upper limit is dictated by the amount of power available and the structural limits of the hog assembly.
Because hog hammers are rigidly attached to the disk assembly or drum, there is a greater possibility of damaging the machine when the hog hammers contact material which cannot be readily broken upon impact. Because of possible machine damage, hog hammers do not normally protrude radially outwardly as far as free-swinging hammers. A large protrusion would also require much more power to force the hammer through the material. Typically, a hog hammer would protrude only about half as much as a free-swinging hammer. The resulting reduction in material contact area can push the material away from the hog hammer head rather than draw it into the disk assembly or drum, reducing the productivity and efficiency of the machine.
The related art does not disclose a waste processor which combines the attributes of a chipper, hammer mill and hog. However, one design has attempted to combine the attributes of a hog hammer with a hammer mill. This design provided for a limited swing of the free-swinging hammer. The design provided for the swinging hammer to protrude above the disk assembly the same distance as the typical free-swinging hammers, but the backward swing or recoil is restricted by a dead stop, wherein a portion of the hammer still protrudes radially outwardly from the disk assembly. At this point, further movement of the hammer is stopped and the swinging hammer has the attributes of a hog hammer.
This compromise arrangement enables the hammers to initially make good contact with the material being processed while using the large amount of kinetic energy stored in the disk assembly to do the work on the material. One disadvantage of this compromise arrangement is that the hammers receive two blows. The first blow occurs when the hammer impacts the material, but a damaging blow may occur when the hammer makes contact with the dead stop. A second disadvantage is that the hammer tip must be designed so that the hammer presents an impact face to the material in its laid back position that will not push the material away from the hammerhead. The required hammer profile for this arrangement rapidly changes shape as the hammer wears, resulting in a loss of performance.